This, coupled with insurance claims arising from cable failures, makes electrical systems and their associated materials a leading area for technology research and innovation to drive down the cost of energy.
In our Charles Parsons Technology Centre in Blyth, ORE Catapult operates the UK’s only state-of-the-art, open-access high-voltage (HV) insulation materials laboratory for the testing and validation of HV insulation materials used in offshore renewables projects.
We partner with key sector players to understand their future testing needs and, as part of a continued programme of investment to keep our assets at the forefront of industry requirements, the lab has recently been refurbished and enhanced with a cutting-edge suite of spectroscopic and microscopic systems, helping our scientists carry out atomic-level characterisation and forensic analysis on the materials that make up offshore power systems.
“You need to know what a material’s made up of, how strong it is, how it performs, and whether it’s meeting its specification,” says Lee Harris, the Catapult’s HV Materials Engineer and the man in charge of the day-to-day running of the lab.
“The next generation of offshore wind farms will need to keep generating reliable electricity for their entire lifespan, which is expected to be around 25-40 years,” says Lee. “For that to happen, the cables that connect the turbines to each other and to the substations are going to have to withstand enormous loads and remain operational in the harsh conditions you find in deep water far offshore.”
The Catapult helps ensure that its clients’ materials are up to that task by putting them through highly-accelerated life testing (HALT) – the process of subjecting something to years’ worth of operational conditions in a condensed period of time, allowing faults and weaknesses to be exposed before the product goes into the field.
For subsea cable manufacturers, like the Catapult’s long-time testing partner JDR, that’s especially important because of the cost of repairs once cables are installed.
“Factor in turbine downtime,” says Lee, “plus the cost of cables, trenching equipment, vessels and personnel and it can cost £2-5million per km. A fault, such as a cable short-circuit, could prove massively costly for developers: insurance claims relating to cable failure alone cost the industry £60m per year.
“There’s a lot of research currently being performed on the performance of cables, how the water ingresses and diffuses over time, and how that affects the cable’s insulating layer quality. One way that cables break down is due to what’s known as a ‘water tree,’ so analysing these is a major part of that research.”
Water trees need only be microns wide to cause a short circuit, and they only form when the water content of a cable’s insulating compound reaches a certain level. “That’s why it’s so important to know the water content,” says Lee. “It’s only when it’s above around 70% that you start to get breakdown effects.
“Carrying out that water tree characterisation gives us an understanding of the condition of the aged insulation and helps us confirm that the insulating layer is high-quality, which in turn helps to keep down the lifetime costs of the offshore wind farms using those cables.”
The laboratory also carries out forensic analysis of materials, with the capabilities to analyse why a breakdown has occurred and factor in the wider set of circumstances leading to a failure. One unique feature of the Materials Laboratory sets it apart from competing facilities: it’s the only open-source, UKAS-accredited lab in the UK with the capability to carry out the full ageing and materials analysis workflow under one roof. That presents a huge advantage for cable manufacturers seeking certification for their insulation products via hot set testing, a process required for conformance to international cable standards. It looks at how strong the insulating material’s bonds are.
“These cables,” says Lee, visibly enthused as he points towards an ageing tank in the Catapult’s HV lab, “will be in this tank for two years undergoing highly-accelerated testing. As soon as we remove the cable from the water, the insulating material starts to push water out – that’s the nature of the compound. So, as per international standards, hot set testing has to be carried out within 15 minutes of the cable leaving the tank.
“With the Materials Laboratory and the HV lab together, it makes our facility the only open-source, UKAS-accredited facility in the country that can carry out that electrical ageing and then materials analysis within the allotted time.
“We’ve worked on projects with both large multinationals and smaller, local companies – open-source labs like this offer a lifeline to companies who don’t have the facilities to carry out these tests themselves. And we have a really strong combination of electrical and materials testing ability that allows us to develop full-workflow solutions.
“In fact, there are few other open-source laboratories in the world with the capabilities that we have here.”